The Laboratory for Sleep and Circadian Rhythms Research is a new Component of the University of Pennsylvania -Philadelphia Geriatric Center CRC that has been developed to address some of the compelling issues in this field which impact on the geriatric population. The timing of this development is highly appropriate in light of the striking developments in the formation of the Center for Sleep and Respiratory Neurobiology (CSRN) at the University of Pennsylvania. The long term goals of the laboratory include studies of the reciprocal interactions between circadian rhythms and both chronic medical illness and depression. The initial focus involves two specific research protocols which relate to established programs of the co-investigators in this Laboratory. Additionally, pilot efforts will be initiated to develop physiological and behavioral assessment techniques that are applicable for studying the chronically ill, frail elderly residents of the nursing home sites of the CRC. Project one represents an extension of a recently funded grant examining multifactorial issues associated with excessive daytime sleepiness (EDS) in elderly subjects. The present project targets depressed elderly subjects who are subdivided on the presence or absence of EDS as determined by questionnaire based interviews. Detailed assessments will include full overnight polysomnography (PSG) and daytime measures of sleepiness and performance on the basis of behavioral measures, performance vigilance task (PVT) testing and multiple sleep latency testing (MSLT). This project examines the hypothesis that EDS associated with depression represents an important comorbidity issue. Understanding the variables related to EDS in elderly depressed subjects may help to identify logical strategies for treating patients who are struggling with this combined burden. Project two will address the effects of discontinuation of chronic benzodiazepine therapy on PSG monitored dimensions of sleep continuity and sleep architecture and on daytime cognitive, performance and behavioral measures in elderly subjects. Patients will be evaluated at baseline, on a stable regimen of benzodiazepine therapy, after acute discontinuation of the benzodiazepine and again 3 months after drug discontinuation. This study will address the hypothesis that discontinuation of long-term benzodiazepine therapy is associated, in some patients, with prominent disruption of sleep continuity. Alternative strategies will be explored to improve the quality of sleep in these patients.